Correlation between self-ignition of a dust layer on a hot surface and in baskets in an oven

International audienceEvaluation of self-ignition hazard of bulk materials requires experimental determination of self-ignition temperatures as a function of volume. There are two standardised methods : determination of the self-ignition temperature of dust samples in oven and measurement of the self-ignition temperature of a dust layer deposited on a hot surface. Sometimes, the sample behaviour during these tests makes the second method difficult to apply. The self-ignition phenomena in these two tests rely on the same principles. Their results are interpreted with the help of theoretical relations. The correlation described in this paper can be considered acceptable to deduce self-ignition temperature of a dust layer, based on results of self-ignition of the same dust in heating ovens, if the Biot number (alpha) can be estimated. Uncertainty on the correlation is near 30 K. This uncertainty is on the same order of magnitude as the difference in the self-ignition temperature on a hot surface for thickness between 5 and 15 mm

Experimental study of CH4/O2/CO2 mixtures flammability

International audienceThe oxy-combustion process uses CH4/O2/CO2/H2O mixtures at various concentrations, according to the different operation phases. To analyze the risks associated to this process, the safety characteristics of these explosive mixtures have to be taken into account. A literature review showed that some safety features of methane in oxygen or in air were not available. Thus, the flammability ternary diagram of CH4/O2/CO2 mixtures was determined at room temperature and 1 bar pressure. Furthermore, the influence of oxygen content on the explosion severity (Pmax; dP/dt) was investigated. The ternary mixtures were prepared directly in a 20 L spherical test vessel. The concentrations of reactants were adjusted using the relationship between the partial pressure and the molar fraction of gas. The ignition source used was an alumel fusing wire. The flammability limits of methane in oxygen were extrapolated at 5 and 68% vol., by using the established CH4/O2/CO2 mixtures ternary diagram. It also confirmed that when the carbon dioxide concentration increases, the flammability range decreases: no ignition was observed when carbon dioxide content exceeded 73%. A significant influence of the oxygen concentration on the explosion severity has been highlighted for CH4/O2/CO2 mixtures containing respectively 10, 25, 45 and 65% vol. of carbon dioxide. The maximal explosion overpressure and the maximum pressure rise were both measured near the stoechiometry. Maximum values of Pmax and dP/dt measured for a 10% vol. carbon dioxide concentration were 11.2 bar rel. and 5904 bar/s respectively, while they were 3.6 bar rel. and 72 bar/s respectively in the case of a 65% vol. carbon dioxide content in the mixture

Atherosclerosis of the descending aorta predicts cardiovascular events: a transesophageal echocardiography study

PURPOSE: Previous studies have shown that atherosclerosis of the descending aorta detected by transesophageal echocardiography (TEE) is a good marker of coexisting coronary artery disease. The aim of our study was to evaluate whether the presence of atherosclerosis on the descending aorta during TEE has any prognostic impact in predicting cardiovascular events. MATERIAL AND METHODS: The study group consisted of 238 consecutive in-hospital patients referred for TEE testing (135 males, 103 females, mean age 58 +/- 11 years) with a follow up of 24 months. The atherosclerotic lesions of the descending aorta were scored from 0 (no atherosclerosis) to 3 (plaque >5 mm and/or "complex" plaque with ulcerated or mobile parts). RESULTS: Atherosclerosis was observed in 102 patients, (grade 3 in 16, and grade 2 in 86 patients) whereas 136 patients only had an intimal thickening or normal intimal surface. There were 57 cardiovascular events in the follow-up period. The number of events was higher in the 102 patients with (n = 34) than in the 136 patients without atherosclerosis (n = 23, p < 0.01). The frequency of events was in close correlation with the severity of the atherosclerosis of the descending aorta. Fifty percent of the patients with grade 3 experienced cardiovascular events. Excluding patients with subsequent revascularization, the multivariate analysis only left ventricular function with EF < 40% (HR 3.0, CI 1.3–7.1) and TEE atherosclerotic plaque >=2 (HR 2.4, CI 1.0–5.5) predicted hard cardiovascular events. CONCLUSION: Atherosclerosis of the descending aorta observed during transesophageal echocardiography is a useful predictor of cardiovascular events

Aortic valve replacement with the minimal extracorporeal circulation (Jostra MECC System) versus standard cardiopulmonary bypass: A randomized prospective trial

AbstractBackgroundWe prospectively evaluated a newly introduced minimal extracorporeal circulation system (Jostra MECC System; Jostra AG, Hirrlingen, Germany) for aortic valve surgery.MethodIn a prospective, randomized study, 100 patients underwent aortic valve replacement either with standard cardiopulmonary bypass (n = 50, group B) or with the MECC System (n = 50, group B). The myocardial protection and the left vent were identical for the two groups. The intrapericardial suction device was never used (only the cell salvage device was used) to reduce the air-blood contact area.ResultsNo significant differences were noted in patient characteristics and operative data between groups. Operative mortality (<30 days) was 2% for group A and 4% for group B (difference not significant). From the preoperative period to the postoperative period, the increase in C-reactive protein was significantly higher for group B (P < .001). The postoperative troponin I level was significantly lower in group A (mean 4.65 ± 2.9 μg/L at 24 hours) than in group B (8.2 ± 4.4 μg/L, P < .03). On the other hand, the MECC System was associated with platelet preservation. Renal function was better preserved and the neurologic event rate was significantly lower for the MECC group (P < .02).ConclusionThe MECC System is safe and allows aortic valve replacement under the most favorable conditions. The system is more biocompatible than standard cardiopulmonary bypass and provides a good postoperative biologic profile and good clinical results, particularly for high-risk patients

Arrhythmic mitral valve prolapse in 2023: Evidence-based update

Patients with mitral valve prolapse (MVP) may develop ventricular arrhythmias, ranging from premature ventricular contractions through more complex non-sustained ventricular tachycardia to sustained life-threatening ventricular arrhythmias. The prevalence of MVP in autopsy series of young adults who died suddenly has been estimated to be between 4% and 7%. Thus, “arrhythmic MVP” has been reported as an underappreciated cause of sudden cardiac death, leading to a renewed interest in the study of this association. The term “arrhythmic MVP” refers to a small subset of patients who have, in the absence of any other arrhythmic substrate, MVP, with or without mitral annular disjunction, and frequent or complex ventricular arrhythmias. Our understanding of their coexistence in terms of contemporary management and prognosis is still incomplete. While literature regarding the arrhythmic MVP may be contrasting despite recent consensus document, the present review summarizes the relevant evidence concerning the diagnostic approach, prognostic implications, and targeted therapies for MVP-related ventricular arrhythmias. We also summarize recent data supporting left ventricular remodeling, which complicates the coexistence of MVP with ventricular arrhythmias. As the evidence for a putative link between MVP-associated ventricular arrhythmias and sudden cardiac death is scarce and based on scant and retrospective data, risk prediction remains a challenge. Thus, we aimed at listing potential risk factors from available seminal reports for further use in a more reliable prediction model that requires additional prospective data. Finally, we summarize evidence and guidelines on targeted therapies of ventricular arrhythmias in the setting of MVP, including implantable cardioverter defibrillators and catheter ablation. Our review highlights current knowledge gaps and provides an action plan for structured research on the pathophysiological genesis, diagnosis, prognostic impact, and optimal management of patients with arrhythmic MVP

Medical and surgical outcome of tricuspid regurgitation caused by flail leaflets

AbstractObjectiveWe sought to evaluate the medical and surgical outcome of tricuspid regurgitation caused by flail leaflets.MethodsWe analyzed the cause, clinical presentation, outcome, and natural history of 60 patients with tricuspid regurgitation caused by flail leaflets, a cause of mostly severe and organic tricuspid regurgitation, diagnosed by means of echocardiography between 1980 and 2000.ResultsThe main cause was traumatic (62%). Clinical presentation was often severe: 57% were symptomatic, 33% had a history of congestive heart failure, and 40% had a history of atrial fibrillation. Compared with expected survival of the US matched population, excess mortality (39% ± 10% at 10 years or 4.5% yearly, P < .01) was observed. Even patients asymptomatic at presentation experienced high tricuspid-related event rates (at 10 years, 75% ± 15% had symptoms or heart failure, atrial fibrillation, surgical intervention, or death). In those patients severe enlargement of right-sided chambers was predictive of poor outcome (at 5 years: 86% ± 9% vs 39% ± 11%, P < .01) independent of cause (P = .31). The poor medical outcome was further confirmed by high event rates (69% ± 9% at 15 years) in the natural history beginning from the flail's occurrence. Tricuspid operations were performed in 33 patients (55% ± 7% at 5 years), with valve repair in 82%, low mortality (3%), and, despite frequently refractory atrial fibrillation, symptomatic improvement in 88%.ConclusionTricuspid regurgitation caused by flail leaflets is a serious disease associated with excess mortality and high morbidity. Tricuspid valve repair can often be performed with low risk, allowing symptomatic improvement. These results suggest that surgical intervention should be considered early in the course of the disease before the occurrence of irreversible consequences

Use of echocardiography in the management of congestive heart failure in the community

AbstractObjectives. We evaluated the use and the impact of echocardiography in patients receiving an initial diagnosis of congestive heart failure in Olmsted County, Minnesota, in 1991.Background. The American College of Cardiology/American Heart Association clinical practice guidelines recommend echocardiography in all patients with suspected congestive heart failure. No data are available on use and impact of echocardiography in management of congestive heart failure in a community.Methods. The medical records linkage system of the Rochester Epidemiology Project was used to identify all 216 patients who satisfied the Framingham criteria for congestive heart failure. Of these, 137 (63%) underwent echocardiography within 3 weeks before or after the episode of congestive heart failure (Echo group), and the other 79 patients constitute the No-Echo group.Results. The No-Echo group patients were older (p = 0.022), were more likely to be female (p = 0.072), had milder symptoms (p = 0.001) and were less often hospitalized at diagnosis (p = 0.001). Fewer patients in the No-Echo group were treated with angiotensin-converting enzyme inhibitors (p = 0.001). Advanced age (≥80 years), lower New York Heart Association functional class, absence of a fourth heart sound on examination, absence of cardiomegaly or signs of congestive heart failure on chest radiography and absence of known valve disease were independently related to the decision not to obtain an echocardiogram. Survival after adjustment for age, functional class and gender was lower in the No-Echo group than the Echo group (risk ratio = 0.607, p = 0.017).Conclusions. The underuse of echocardiography appears to be associated with poorer survival and underuse of angiotensin-converting enzyme inhibitor therapy

Prospective comparison of speckle tracking longitudinal bidimensional strain between two vendors

SummaryBackgroundSpeckle tracking is a relatively new, largely angle-independent technique used for the evaluation of myocardial longitudinal strain (LS). However, significant differences have been reported between LS values obtained by speckle tracking with the first generation of software products.AimsTo compare LS values obtained with the most recently released equipment from two manufacturers.MethodsSystematic scanning with head-to-head acquisition with no modification of the patient's position was performed in 64 patients with equipment from two different manufacturers, with subsequent off-line post-processing for speckle tracking LS assessment (Philips QLAB 9.0 and General Electric [GE] EchoPAC BT12). The interobserver variability of each software product was tested on a randomly selected set of 20 echocardiograms from the study population.ResultsGE and Philips interobserver coefficients of variation (CVs) for global LS (GLS) were 6.63% and 5.87%, respectively, indicating good reproducibility. Reproducibility was very variable for regional and segmental LS values, with CVs ranging from 7.58% to 49.21% with both software products. The concordance correlation coefficient (CCC) between GLS values was high at 0.95, indicating substantial agreement between the two methods. While good agreement was observed between midwall and apical regional strains with the two software products, basal regional strains were poorly correlated. The agreement between the two software products at a segmental level was very variable; the highest correlation was obtained for the apical cap (CCC 0.90) and the poorest for basal segments (CCC range 0.31–0.56).ConclusionsA high level of agreement and reproducibility for global but not for basal regional or segmental LS was found with two vendor-dependent software products. This finding may help to reinforce clinical acceptance of GLS in everyday clinical practice

Watchful surgery in asymptomatic mitral valve prolapse

The most common organic etiology of mitral regurgitation is degenerative and consists of mitral valve prolapse (MVP). Volume overload because of mitral regurgitation is the most common complication of MVP. Advocating surgery before the consequences of volume overload become irreparable restores life expectancy, but carries a risk of mortality in patients who are often asymptomatic. On the other hand, the post-surgical outcome of symptomatic patients is dismal and life expectancy is impaired. In the present article, we aim to bridge the gap between these two therapeutic approaches, unifying the concepts of watchful waiting and early surgery in a “watchful surgery approach”